Radio receiving apparatus



Nov. 2, 1926. 1,605,333

F. W. DUNMORE RADIO RECEIVING APPARATUS Filed Sept. 4, 1925 2 Sheets-Sheet 1 Nov. 2 1926. 1,605,333

' F. w. DUNMORE RADIO RECEIVING APPARATUS File p 4. 1925 2 Sheets-Sheet 2 Patented Nov. 2, 1926.

UNITED STATES PATENT OFFICE.

RADIO RECEIVING A]?litlitAil'FlJ'S.v

Application filed. September 4:, 1925. Serial No. 54,507.

This invention relates in general to radio receiving apparatus and more particularly to certain novel means for simplifying the operation of such apparatus. 1

An object of my invention is to provide means whereby the electrical constants of one or more circuits may be Varied without causing variations in other circuits. In the use of a compensating condenser on a radio direction finder, I have discovered that the operation of this condenser, especially when operating on high frequencies, completely detunes the direction finder coil, rendering it necessary to retune with the coil tuning condenser and thus presents complications in the operation of the device.

Another object of my invention is to provide means for varying the balancing condenser of a radio direction finder or coil antenna without detuning the direction finder or coil aerial circuit becoming detuned.

A further object of my invention in which the operation of adjusting one or more radio circuits may tend to upset the adjustment of one or more circuits, and cause the capacities or inductances which are properly connected to these circuits to become upset is to provide means for varying the capacities or inductances in such a manner that the circuits will remain in fixed adjustment.

It is therefore proposed to provide a balancing condenser with a shaft adapted to carry a specially shaped cam, the device as a whole being so arranged that the cam will operate a retuning condenser connected across the direction finder or coil antenna tuning condenser, the tuning condenser operating to keep the direction finder or coilantenna always 'in tune as the compensating condenser is varied over its range. This result is also accomplished by means of a cam operated variable inductor connected in the direction finder or coil antenna circuit.

With the foregoing and other objectsin view, my invention resides in the combination of parts, and in the details of construction hereinafter set forth with particularity in the following specification and appended claims, certain embodiments of my invention being illustrated in the accompanymg drawin s, in which: i

ig. 1 illustrates diagrammatically one form of my invention,

Fig. 2 shows another form in which the condenser is replaced by a variable'retuning inductor,

Fig. 3 shows the application of the form of my device as shown in Fig. 1 applied to a plurality of circuits,

Fig. 4 shows the application of that form of my invention. shown in Fig. 2, to a plurality of circuits.

Fig. 5 shows a form of my invention in which the constants of the first circuit are variable by means of a variable air condenser in place of a variable inductor.

Fig. 6 shows a form of my invention in which a compensating inductor is used in place of a compensating condenser.

Referring more particularly to the drawings, Fig. 1 shows an application in which the detuning efiect of a balancing condenser connected across a direction finder or coilantenna is automatically compensated for by a cam operated condenser. By way of example I will take the ordinary direction finder circuit in which 6 is the direction finder coil, 7 is the tuning condenser, 15 the amplifier. The three-plate balancing condenser 2 is connected across the tuning condenser 7 with the center plates of the condenser 2 grounded at G.

Normally when condenser 2 is operated by the diall to sharpen the minimum, this variation detunes the coil 6 which has to be retuned by readjusting the condenser 7. This constant juggling between condensers 2 and 7 to' obtain a sharp-minimum and yet maintain the coil 6 in tune is very awkward. To

overcome this difficulty, I provide a cam 3 which rotates with the shaft of balancing condenser 2. This cam 3 operates an arm 4 which in turn operates a retuning condenser 5, which due to the particular shape of the cam 3, operates in such away as to add or subtract an amount of capacity to condenser 7 equal to that subtracted or added by the operation of condenser 2.

The proper shape of cam 3 is readily determined as follows: Arm 4 is slipped off of disc 3 and condenser 5 set at about threefourths its maximum capacity by means of an adjustment knob 8.. A transmitting or beacon station 15 is then tuned in by means of condenser 7 with condenser 2 set in the half way position, that is with the movable or grounded plates not meshing with either set of fixed plates or meshed equally with both. The position of arm 4 on dial 3 is then marked.

Dial 1 is then turned, for instance, five .degrees in a clockwise direction. This operation detunes the coil 6. The signal is tuned in again by adjusting the condenser 5 by means of the knob 8. The new position of arm 4 on cam 3 is then marked. This process is repeated every five degrees over the complete 180 angle of rotation of condenser v maintained in tune by the proper variationof condenser 5. It is of course understood that the adjustment of the knob 8 is necessary only while determining the shape of the cam 3.

Another method of producing the same result is shown in Fig. 2 in which condenser 5 is replaced by variable returning inductor 9. The principle of operation is the same except that coil 6 is retuned by'the variable retuning inductor 9 instead of the retuning condenser 5. The shape of cam 3 is also determined as described above.

Another application is shown in Fig. 3 in which means are provided whereby when the electrical constants of one or more circuits, in this case the circuitlO-ll, are varied, such variation does not upset the constants of another circuit or circuits, in this case circuit 12-13.

Suppose the circuit 10-11 to be so related to the circuit 12-13 either by reaction due to coupling between the two or otherwise that the adjustment of circuit 10-11 upsets the constants of circuit 12-13. Tocompensate for such reaction and maintain the constants of the circuit 12-13 undisturbed while the constants of circuit 10-11 are varied by the variable inductor 11, I place a cam 3 roperly shaped on the shaft of 11 whic serves to operate a retuning condenser 5 in such a way to compensate for 'the reaction of circuit 10-11 on circuit Fig. 4 shows a combination in which a variable compensating inductor 9 is used in place of compensating condenser 5, the effect being to compensate for the reaction of circuit 10-11 on circuit 16-13.

Fig. 5 shows a combination in which the constants of the first circuit are variable by means of a variable air condenser 10 in place of a variable inductor. The variations of this circuit 10-14 are prevented from upsetting the constants of circuit 12-13 by means of a compensating condenser 5 operated by a cam on the variable air condenser shaft.

Fig. 6 shows another combination in which a compensating inductor 9 is used in place of a compensating condenser, said compensating inductor being operated by a cam on the shaft of a variable air condenser shaft.

1 claim:

1. The combination in an apparatus for receiving radio signals of a balancing condenser connected across the terminals ot' a radio direction finder coil and tuning condenser, a cam operated by said balancing condenser, a second tuning condenser connected in parallel with the first tuning condenser and operated by said cam.

2. The combination in an apparatus for receiving radio signals of a balancing condenser connected across the terminals of a radio direction finder coil and tuning condenser, a cam operated by said balancing condenser, a variable impedance connected in the direction finder coil circuit, said variable impedance being operated by said cam in such a manner as to counteract the detuning eflect produced on the direction finder circuit when the balancing condenser is operated.

In testimony whereof I atfix my signature.

FRANCIS W. DUNMORE. 

